Cytological Problems. 229 
does not affect the development of the male haploid generation, 
whereas on Correns* hypothesis half the microspores being female 
should produce female gametophytes 1 . 
When the close resemblance of the higher plants and the 
Metazoa is considered, the same conclusion should apply to 
animals, where usually the diploid as well as the haploid generations 
are distinct sexually. The reducing division should clearly separate 
the same characters or tendencies in both higher animals and higher 
plants. The phylogenetic considerations upon which Strasburger 
lays stress should clearly be taken into account in framing theories 
of sex; while experimental results are of the first importance, the 
conclusions drawn from them should be applicable to such classes 
as homosporous ferns, heterosporous ferns, and dioecious angio- 
sperms. Strasburger is further of the opinion that the sex-characters 
will not be found to obey the Mendelian rule of segregation. He 
bases this view mainly on the facts of parthenogenesis, and the 
observation that commonly dioecious plants may bear branches with 
flowers of both kinds, or, under the action of special stimuli, 
hermaphrodite flowers. It is not, however, at all clear what 
becomes of the minor dose of maleness which, on this hypothesis of 
Noll and Strasburger, the females receive. Strasburger accepts the 
view that the egg-cells all bear femaleness, and relates this to the 
fact that only one egg-cell results from the tetrad. There seems no 
reason, however, why the egg should not have an equal chance of 
carrying either maleness or femaleness. Phylogenetic considerations 
would appear to lead to something of the nature of Castle’s original 
suggestion, that both sexes are heterozygotes. 
The next point dealt with by Strasburger is the question of the 
apogamous development in Mercurialis and Cannabis described by 
Kruger. He was unable to confirm these observations; female 
plants of the two forms kept in a closed greenhouse failed to set 
seed. Cytological examination also failed to support the view that 
these forms develop without fertilisation. 
The author next turns to the question of the “ false hybrids ” 
of Millardet, which completely resembled the male parent. 
Millardet’s observations were made in 1894, but since then Solms- 
Laubach has made the cross Fragaria virginiana ? X F. elatior $ , 
and found that the resulting offspring resembled almost exactly the 
$ parent; they were, however, completely sterile. As these cases 
are of particular genetic interest, Strasburger investigated the 
histology of the pollination-process and found it perfectly normal, 
with a regular fusion of the two nuclei. The only interpretation 
appears to be that the whole of the characters of one parent are 
dominant over those of the other. 
The next section of the paper deals with the cytology of 
Wikstrcemia indica which was shown by H. Winkler in 1904 to be 
apogamous and to have abortive pollen grains. The somatic cells, 
as seen in the tapetum of the anthers and the nucellus and integu¬ 
ments of the ovules, were of particular interest. The resting nuclei 
of the tapetal cells showed a variable number of granules, rarely 
as many as 20; their number was inversely proportional to 
their size. In division-stages of integuments, etc., chromosomes 
in numbers as low as 6, 7, 9 and 10 were found, though the normal 
number is 52, since 26 gemini (pairs) are to be seen in the reducing 
1 It is possible that sex of gametophyte and sex of sporophyte 
are not quite comparable. 
